3M High-Temperature Flue Tape 2113NA (rated to +600F). You can usually find it at hardware stores if you look carefully (I've never found it with the rest of the adhesive tapes), and on-line of course. If the foil tape doesn't give a temperature rating, it's more likely to be foil duct tape rated to +250F, used for taping hot air ducts. (Not to be confused with the ubiquitous fabric duct tape, which is used for taping cold air ducts and everything else.)
For my cozies, made from a closed-cell sleeping pad, I just used plastic box-sealing tape. It worked.